In this paper, based on the remote sensing image data, the hydrological data from 1987 to 2016, and the high-resolution topographic data, we extracted the wetland vegetation information of the Lake Dongting and constructed the multi-cycle water level fluctuation measurement. On this basis, stepwise regression method and polynomial fitting were used to estimate the key hydrological variables and to quantify the effects of hydrological process on the two typical wetland vegetation. The main conclusions as follows: 1) From 1987 to 2016, the area of the whole vegetation had a significant increasing trend in the whole wetland, especially the Populus euramevicana community. And in East Lake Dongting, the Phragmites australis community occupied the space of Carex brevicuspis community, which promoted the whole beach to the center of the lake. 2) Water level fluctuation in flood season was the determinant towards the distribution of Carex brevicuspis and Phragmites australis. There was a non-linear response of water regime to the area of Carex brevicuspis. When the average water level was about 29 m during flood season, it will be most suitable for the growth of Carex brevicuspis. For the Phragmites australis community, low flow in flood season was more favorable for its growth and development. Water level fluctuation during rising and retreating season were the secondary important regime factor influencing the distribution of wetland vegetation in East Lake Dongting. Lower water level in the two season can facilitate the distribution of Phragmites australis.